In thermal management systems of current high-power LED products, a passive cooling device is the most commonly used means. In this type of thermal management systems, the following performances of a cooling body of the passive cooling device will affect it: heat dissipation including a surface emissivity and convection ability; and thermal conductivity (coefficient of thermal conductivity).
A known cooling body for a cooling device is made from an aluminum alloy-384 by die casting. In the consideration of anti-corrosion and beauty, usually surface treatment will be performed for the cooling body, for example, coating paint. The cooling body has an advantage of high surface emissivity, for example, it is about 0.92-0.96 in the case that paint is coated. However, the thickness of the surface layer is large and the coefficient of thermal conductivity is also low, for example, in the case that paint is coated, the thickness is about 0.2-0.8 mm and the coefficient of thermal conductivity is less than 1 W/m*k. Meanwhile, due to the material characteristics of the aluminum alloy-384, the coefficient of thermal conductivity is not high, being about 92 W/m*k.
In the prior art, the cooling body of the cooling device is usually made from the aluminum alloy-6063 by an extrusion molding process. After the extrusion molding process, its surface should be subjected to oxidization treatment to form a layer of thin oxidization film which is about 0.02 mm.
The oxidization film has a middle coefficient of thermal conductivity being about 46 W/m*k. However, due to the material characteristics of the oxidization film, its surface emissivity is low being about 0.20.
In addition, the prior art also discloses a cooling body made from an aluminum nitride material, and the surface treatment to the cooling body made from the aluminum nitride material is only to clean the surface. The surface of the cooling body is a normal aluminum nitride ceramic surface and has no any additional material. The cleaned surface has no any coating. Therefore, the overall cooling body has the same high coefficient of thermal conductivity, being about 180 W/m*k. Meanwhile, the surface emissivity of the cooling body is also high, being about 0.93. However, its disadvantages are also obvious, that is, the material cost is high and the making thereof is difficult.